Associate Social Development and Employment Minister Tariana Turia is condemning a bus company's rule that workers can only speak English at work, even during breaks.
Tramways Union Secretary Kevin O'Sullivan said Mana Coach Service's position was unacceptable but negotiations had failed to get it changed.
The company, in its companyhandbook, required all staff to communicate using English when writing reports, in general conversation in the depot and in the driver's room.
Mana Coach Services runs bus services from Paraparaumu, Porirua and Newlands, north of Wellington.
Mr O'Sullivan said his union represented about 30 workers at the company which employed approximately 130 staff.
"The company employs lots of people for whom English is a second language for them," he told NZPA.
He said staff should be able to feel at ease in breaks.
Mr O'Sullivan said the Human Rights Commission had told the company it was potentially in breach of the Human Rights Act but neither that nor union submissions had made any difference.
Under the law workers can be required to speak English for health and safety reasons.
Maori Party co-leader Mrs Turia said the rule was a kick in the face for Polynesian and Maori workers.
"It's outrageous that a company based in the Wellington region's Polynesian capital has told its workers they can only speak to each other in English even when on a break in the staff tearoom," she said.
"What makes it even worse is that the company hierarchy has tried to justify their policy by saying they find it threatening when hearing workers talk to each other in another language that's not English, the days of being seen but not heard are over."
One News broke the story last week after an earlier report saw Thorndon New World dump a similar rule.
